This invention relates to mechanical assemblies that regulate the temperature of an electronic device, such as an integrated circuit chip, by pressing a temperature controlled heat exchanger against the chip.
In the prior art, one assembly of the above type is described in U.S. Pat. No. 4,791,983 which is assigned to the assignee of the present invention. The assembly in patent '983 uses a coil spring 20 to press a planar surface of a liquid cooling jacket against a planar surface of an integrated circuit chip. More specifically, the coil spring 20 is compressed in a direction perpendicular to the planar surfaces of the liquid cooling jacket and the integrated circuit chip to squeeze those surfaces together and thereby lower the thermal resistance between them.
Due to various manufacturing tolerances, the planar surface of the integrated circuit chip (to which the cooling jacket mates) can be oriented at different angles and different heights relative to a nominal position. To accommodate these variances, the assembly in patent '983 includes a guidepost 18 which is attached to the cooling jacket, extends perpendicular to the mating faces of the cooling jacket and the integrated circuit chip, and is loosely held by a beam 14. This guidepost, together with the coil spring and the cooling jacket, can tilt at different angles and move to different heights to thereby accommodate the variations in the orientation of the integrated circuit chip.
With the assembly of patent '983, it is desirable for the coil spring to have a small spring constant. That is because when the planar surface on the cooling jacket initially contacts the planar surface on the integrated circuit chip, those two surfaces will be at different angles, so contact will initially occur at a single point on the corner of the chip. If the coil spring has a small spring constant, then the force that is exerted at the initial point of contact will be small and the chances of cracking the corner of the chip will be reduced.
On the other hand, to insure that the thermal resistance between the mating surfaces of the cooling jacket and the chip is sufficiently small, the final force with which those two surfaces are pressed together must be large. Thus to achieve this large final force with a small spring constant, the coil spring 20 must have a long length. However, increasing the length of the spring 20 inherently increases the minimal distance with which several of the assemblies can be placed side-by-side in a rack within an end-product.
Also, after initial contact occurs between the planar surface of the cooling jacket in patent '983 and one corner of the chip, the cooling jacket must pivot on the guidepost to make the cooling jacket lie flat against the chip. However, in order for the cooling jacket to pivot on the guidepost, its planar surface must slip on the chip at the initial point of contact. And, such slippage between the cooling jacket and the chip can damage the chip.
Further with the assembly of patent '983, the planar surface of the cooling jacket can become twisted and/or offset relative to the planar surface of the chip. To accommodate the above problem, the planar surface of the cooling jacket can be made substantially larger than the planar surface of the integrated circuit chip. But, such an increase in the size of the cooling jacket will be prohibited if the chip is held by a socket which the enlarged cooling jacket can hit, or another component lies next to the chip which the enlarged cooling jacket can hit.
Accordingly, a primary object of the present invention is to provide an improved mechanical assembly for regulating the temperature of an integrated circuit chip in which all of the above drawbacks with the prior art are overcome.